So im finding the original burning of king olaf in king olaf's tomb and I'm helping the spirit of the bard who wrote the the song fight off a horde of draugr when king olaf himself pops out of the main casket ready to fight. I said to my self "lets do this" and my follower, the spirit and I fought king olaf together until he was dead. Having gotten his revenge the spirit faded away and I was all warm and fuzzy.

Fast forward a long while and I make it to the steps of Soverngard and enter and who do I find inside other than king olaf who has now forgiven the bard and is eagerly waiting for his spirit to make it to soverngard so he can apologize or whatever. Olaf had obviously been there for a long time, long before alduin showed up.

So my question. Who are the draugr? Are they completely soulless automatons? Are the people that they once were long since gone and have been replaced with something else and if so with what? I always thought they were dragon disciples from the dragon cult but king olaf was himself a dragon fighter and captured numninex so why is he a draugr? Did that spirit not actually get any revenge whatsoever since all the draugr he was fighting did not actually contain the souls of the people who wronged him?

They can't be souless automatons, becouse they have (white) soul, thus can be soultraqed. Maybe the Draugr are only the part of being that have been dead. King Olaf is great example. In Sovengrade you can talk to him, while in his tomb he will attack you on sight (like most Draugr). Maybe the Draugr are the leftovers of your worst features ?

Good theory. As you said they can't be completely soulless, however you can only get white souls from them.
Maybe the more 'human part' of their soul goes to Sovangard.. While the lesser, more primal parts of their souls are left in their bodies?